Neuroscience, like many fields, is limited by the technology available to dissect complex cellular and biochemical processes. Further elucidation of neurophysiology requires methodology for the conditional perturbation of individual components of the underlying molecular and cellular networks. This proposal is directed toward the development of small-molecular probes that will allow for the conditional modulation of multifunction, pre- and post-synaptic proteins, and the signal transduction pathways regulated by neurotransmitter. To accomplish this goal we will: 1) assemble, express, and purify a collection of synaptic proteins after using computational tools to identify key sequence elements and functional domains; 2) identify small-molecule probes that selectively bind to each protein by performing over 3 million high-throughput binding assays using small-molecule microarrays composed of chemicals derived diversity-oriented organic synthesis and known bioactives; 3) validate the observed in vitro binding interactions using surface plasmon resonance analysis; and finally, 4) to characterize the phenotypic effects of the small-molecule probes using neuronal cultures, fluorescence microscopy and genetically-encoded fluorescent reporters to measure synapse assembly, synaptic vesicle dynamics, and synaptic signaling. Developing small-molecule probes, and improving the technologies for their discovery, will expand the molecular toolkit available for dissecting complex neuronal processes, including those implicated in neurological disorders and psychiatric disease. Small-molecule probes provide the opportunity to dissect the complex functions of proteins and molecular networks regulating neurophysiology. Besides increasing our understanding of the cell biology of the synapse, these findings will ultimately enable a better understanding of the relationship between brain chemistry and behavior, as well as to better understand the causes of neuropsychiatric and neurological diseases. In the future chemical biology in general, and chemical genetics in particular, will play an important role in catalyzing new discoveries and potentially insight into function of the nervous system.